Copies of Jim Wark's aerial photos of the Lewis and Clark Trail
are available from AirPhotoNA.com.
In this photo of the lower Marias River, taken by Jim Wark in July of 1999, the water looks relatively clear, especially in the shallows around the sandbars. During the first week in June, 1805, however, this was the river that challenged the Corps' "cogitating faculties" because, as Lewis conceded, it apparently gave to the Missouri "the colouring matter and character which is retained from hence to the gulph of Mexico." Indeed, he reassured himself that it had "every appearance of the Missouri below except as to size." In other words, it was muddy then. And it's still brownish today above the reservoir, Lake Elwell, before the silt settles out behind Tiber Dam.
For an extensive treatment of the land of the Marias River, see Marias River.